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  #1  
Old 02-21-2006, 02:51 AM
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Join Date: Feb 2006
Posts: 117
1981 mercedes 380sl climate control

Greetings,
I just bought a 1981 mercedes benz 380 sl and having issues with the climate control.
Heater:
when I turn the temp wheel to 85 with the ac switch on off and hit auto lo or auto hi, no heat comes out, blower doesen't blow. I can turn on ac switch and turn it off and then cold air starts blowing, but only cold air and it is blowing everywhere except for the three vents in the center. Defrost and bilevel also blow cold air.
A/C:
A/C works and cools fine except no air comes out from the three center vents.

What I've done to troubleshoot:
1. Tapped on the climate control servo in the engine compartment (it stamped manufactured in USA). Checked all vacuum line.
2. Check and replaced the fuse in the passenger compartment.
3. Pulled off the center console and double check all wiring (to my best abilities).
4. Checked the vaccum line on the driver compartment, even unplugged everything and had the green hose go direct to the intake. Still same problem.
5. There is a clicking noise coming from what appears to be a cylinder thingy at the foot of the passenger compartment. Mounted on the firewall.
There is three of those things in a row with what appears to be a vacuum line coming out of it.
  #2  
Old 02-21-2006, 08:25 AM
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Join Date: Mar 1999
Location: Tucker, Ga USA
Posts: 12,153
IF you can't get heat in DEFROST then the servo is the most likely problem.

Check out the ad in the SL forum for un-wired tools.. they have a kit to by-pass you old non-functioning servo.
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  #3  
Old 02-22-2006, 01:01 AM
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Join Date: Feb 2006
Posts: 117
but isn't true that if the servo was bad I would get cold air blowing out of the vents with the ac off and the temp set to 85?
In addition, if that was the case how can I bypass the servo with a mechinical vaccum pump.
I thought the bad part would be the valve/butterfly that opens up the heater/outside air vent?
I will check out the post in the sl gallery.
Thanks bunches.
Dmtiri
  #4  
Old 02-22-2006, 09:19 AM
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Join Date: Dec 2000
Location: Battle Ground, WA
Posts: 576
Not enough vacuum - vacuum leak!

Hi there,
If your blower won't run in the auto-lo or auto-hi positions there isn't enough vacuum to operate the "main" vacuum switch. It's the one with the green body. It requires around 10" of vacuum to operate, and is in series with the blower motor. Usually there is a leaky diaghram on one of the air flap controls. My car had a plugged check valve under the engine hood that was obstructing the vacuum to the heater. If you cannot get heat in the defrost position, the servo unit under the hood is most likely also bad. As MB Doc says, check out the unwired tools servo upgrade, it is the best way to go if you are going to keep the car. The original servo units are unreliable and very troublesome, and can cause your battery to run down if they jam in the wrong position. You can go to the unwired tools web site and download their vacuum diaghrams, which are very helpful in locating vacuum leaks.
__________________
Richard Wooldridge
'01 ML320
'82 300D 4.3L V6/T700R4 conversion
'82 380SL, '86 560SL engine/trans. installed
'79 450SL, digital servo update
'75 280C
  #5  
Old 02-22-2006, 06:07 PM
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Join Date: Feb 2006
Posts: 117
where is this main vacuum switch?
  #6  
Old 02-22-2006, 07:32 PM
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Join Date: Dec 2000
Location: Battle Ground, WA
Posts: 576
Main vacuum sw location...

On my 450SL it was behind the glove box liner. I could see it from underneath, but it was easier to see by removing the glove box liner. It was the one farthest to the right (passenger) side on my 450SL. On my 450SL there were 7 or 8 vacuum switches/controls behind the glovebox.
__________________
Richard Wooldridge
'01 ML320
'82 300D 4.3L V6/T700R4 conversion
'82 380SL, '86 560SL engine/trans. installed
'79 450SL, digital servo update
'75 280C
  #7  
Old 02-24-2006, 06:55 AM
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Join Date: Feb 2006
Posts: 117
I will try to test for a leak in there and look at those switches.
The switch that turns on the three center vents during a/c and turns them off during heating is also in there? or is it the same switch?
  #8  
Old 02-24-2006, 10:00 AM
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Join Date: Dec 2000
Location: Battle Ground, WA
Posts: 576
No....

No, the "switch" that does that is the servo unit, in conjuntion with the pushbuttons. You need to go to the Unwired Tools website and download the vacuum diagrams they have posted there. They are free for the download, and are very helpful in diagnosing vacuum problems. Your vacuum problem could be the servo itself, any of the 7 vacuum pods in the car, the control panel switch, the vacuum feed from the engine to the heater system, a puncture/blockage of any of the lines, etc... I used a mighty-vac to test everything for leakage, using the Unwired Tools vacuum diagrams, which are functionally equivalent to the ones in the factory manual, but much easier to follow.
http://www.unwiredtools.com/accii.html
The heater system is identical to and copied from one that Chrysler used in 1971. Here's a link to the Chrysler manual for it:
http://imperialclub.com/Repair/Lit/Master/281/cover.htm
Good luck with it!
__________________
Richard Wooldridge
'01 ML320
'82 300D 4.3L V6/T700R4 conversion
'82 380SL, '86 560SL engine/trans. installed
'79 450SL, digital servo update
'75 280C
  #9  
Old 02-25-2006, 02:23 AM
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Join Date: Feb 2006
Posts: 117
First let me thank you for your help.
Today I was out checking the vacuum lines (didn't get very far), when I rememebered the mono valve trick, unplug it and heat should come on if it's the mono valve. So I went and smaked it around a little bit in case it was stuck, in the midst of smacking it around I also managed to wack the climate control servo and heat started coming out for the defrost, then when I turned on the a/c the three center vents started working. However, when I hit auto hi or lo without the a/c switch turned on nothing blows, if I just flip the a/c switch to on blower comes on and the the heat works as well. So I am left with two questions:
1. My mono valve has a patch on the top part of it (a piece of rubber with clamp), should I replace the mono valve based on the acting up I have expirienced?
2. When I hit the auto lo or hi buttons without the the a/c switch flipped to the on position nothing blows, if I flip that switch to on and then back to off everything works as it should. Does that sound like a vaccuum problem or a servo problem?

Again thank you all so much I will try to contribute as much as I can to your forum. If anyone has any jeep questions I am sure I can answer those....
  #10  
Old 02-25-2006, 10:17 AM
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Join Date: Dec 2000
Location: Battle Ground, WA
Posts: 576
Your car doesn't have a monovalve!

Hi there,
First, your 1981 380SL DOES NOT have a monovalve. They were used on the climate control systems starting in 1982 and later. The item you are referring to is the auxilliary water pump, a small electric pump used to aid water flow through the heater lines. It is located close to the servo unit, just in front of it, between the servo and the overflow tank.
As I have said before, the reason you do not have any blower action in auto lo and auto hi is a vacuum leak. The "main" switch, sw 19, doesn't have enough vacuum to operate. Turning the AC switch on then off picks the AC relay which then bypasses sw 19 to operate the blower. You need to get a Mighty-vac and start troubleshooting the vacuum leak problem! Did you download those vacuum diagrams from the Unwired tools site? They are a big help when looking for a vacuum leak. It sounds like your servo is indeed bad, if rapping on it got it going temporarily. Keep in mind that the vacuum leak could be at the servo vacuum lines connector, or even in the servo itself.

Regards,
__________________
Richard Wooldridge
'01 ML320
'82 300D 4.3L V6/T700R4 conversion
'82 380SL, '86 560SL engine/trans. installed
'79 450SL, digital servo update
'75 280C
  #11  
Old 02-25-2006, 12:16 PM
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Join Date: Feb 2006
Posts: 117
thanks for the clarification, glad that I didn't go on thinking that was the mono valve (the manuals are on order).

I downloaded the vaccuum diagrams, but after tapping on the servo I was sure that it was the problem. That's why I didn't troublehshoot anymore. In addition I also thought that since I disconnected EVERYTHING except the climate control from the driver side firewall I gave it more then enough vaccuum, but I guess not, so I will try to find the vaccuum line. Forgive the ignorance, but what is a might max?

Thanks again.
  #12  
Old 02-25-2006, 03:25 PM
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Join Date: Dec 2000
Location: Battle Ground, WA
Posts: 576
It's a tool...

A Mighty Vac is a tool - it has a hand operated vacuum pump that's connected to a vacuum gage that you can use to make a vacuum and check for leakage. It can also be used to bleed brakes. You can google on "mighty vac, or look on Ebay to find one. Most auto parts stores carry either the mighty vac or a copy. It is the easiest way to check your vacuum pods for leaks, you just connect the pod's vacuum line to the mighty vac, pump up a vacuum, and check the gage to see if there's a leak.
__________________
Richard Wooldridge
'01 ML320
'82 300D 4.3L V6/T700R4 conversion
'82 380SL, '86 560SL engine/trans. installed
'79 450SL, digital servo update
'75 280C
  #13  
Old 02-25-2006, 05:51 PM
1979300SD 24 years
 
Join Date: Jan 2006
Location: Bourbonnais, Illinois
Posts: 16
Tip

Great spot to look first for a vac leak is on the drivers side door -opening and closing often thru the years creates a crack in one of the vac lines to the locking system. The other spot is under the hood -people knock a line loose when changing the oil filter.
  #14  
Old 03-01-2006, 09:01 PM
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Join Date: Feb 2006
Posts: 117
okay, no vacuum leaks.....
Now I only get heat, so I think my servo is hosed. There is one online with an aluminum case that is $470, the local mechanic says it's a rip off and is encouraging me to buy a conversion kit for $800.
Any suggestions?
  #15  
Old 03-02-2006, 12:47 AM
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Join Date: Dec 2000
Location: Battle Ground, WA
Posts: 576
Too much!

Hi there,
Go to the main Shop Forum menu, then select the SL forum. At the top of the page there is an advertisement for the digital servo upgrade. (Unwired tools logo). Click on it! You can get the latest version of the unwired tools digital upgrade servo from them for $699, or from Performance Products, or from Phil on this website. Your Mechanic has a $100 profit built in to his price!
It is about a 2 hr job to convert to the digital servo. You can download the instructions from the unwired tools website to see if you feel up to the task.
__________________
Richard Wooldridge
'01 ML320
'82 300D 4.3L V6/T700R4 conversion
'82 380SL, '86 560SL engine/trans. installed
'79 450SL, digital servo update
'75 280C
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